How do you suggest one does that? Do you know how much time it takes for a freelancer to complete a day's work? Someone who has a 9 to 5 job wouldn't be able to do freelancing on the side unless they become too disciplined and don't waste any of their time in doing anything extra, and also decides to not give time to their family and loved ones, then maybe it's achievable, otherwise, you can't manage so many things in one day.

You get too exhausted when you get back from work, you take some rest, get up, eat something, and then spend some time with your family, and the day is already over. You can't stay up at nights to do freelancing because you need to go to work in the morning, and if you compromise on your sleeping schedule, it will start affecting your health.

That's why one can barely manage both, and that's why it's always a two-way road, and you will need to choose one. You either choose to do the 9 to 5 job, and maybe do a little something when you got free time, or become a full-time freelancer and leave the job, you can't do both full-time.